I see, hmm
Admit I am terribly short on US Navy and USMC 'between the wars'.
Only book I have is 'Bill' Larkins US Navy 1921-41 combined with USMC 1914-59 and the training units is not the book's raison d'aitre...

Any internet site you can recommend or perhaps a book by yourself could solve my problem??...

Unfortunately, Stig, I am not aware of any useful internet sites or any books, other than the two you mention, that cover the subject in any detail. I suppose that there is not a lot of interest in this area, other than in the colour schemes and markings?